The goals of this project, which remain unchanged, are to: evaluate the efficacy of 1,25(OH)2-vitamin D3 in preventing the development of overt osteodystrophy; to establish quidelines for the use of this agent; identify potential side effects and toxicity associated with such treatment; and identify reasons for other therapeutic intervention. In addition, we hope to characterize the nature of the dialysis bone diseases that are unresponsive to treatment with 1,25(OH)2D3. It is hoped to clarify the pathogenesis of such bone disease and establish the best methods for management.